The present invention relates to a magnetic tape winding method for use in the cases where a magnetic tape is wound onto a tape winding body from a raw magnetic tape roll having the same width as that of the final product, where a magnetic tape already wound on a tape winding body is rewound onto another tape winding body, and where a magnetic tape from a roll of raw tape having a width larger than that of the final product is cut and wound into a plurality of raw tape rolls of the same width as that of the final product.
Processes for manufacturing magnetic tapes such as audio cassette tapes, video cassette tapes, memory tapes, broadcast video tapes, and the like include as intermediate steps, steps such as a take-up step of taking up a magnetic tape of a predetermined length onto a small capacity tape winding body such as a reel, hub or the like from a long roll of raw magnetic tape, a retake-up step of taking up a magnetic tape already wound on a tape winding body so as to rewind it onto another tape winding body, and a take-up step of cutting and taking up a magnetic tape of a raw roll having a width larger than that of the final product into a plurality of rolls of raw tape of the same width as that of the final product.
In the case where a magnetic tape is wound onto a tape winding body in the tape-up and retake-up steps described above, there may occur a problem that due to the physical properties of the roll of the raw magnetic tape at its feed side, the physical properties of the tape winding body at the tape take-up side, and the physical properties of the magnetic tape itself, there occurs a change in tape movements such as vibration of the tape in the directions of its thickness and width, resulting in a problem in the finally wound state of the tape. Specifically, the winding surface (the end edge of the tape) may have an uneven and ragged appearance when observed in the axial direction of the tape winding body. In general, the higher the running speed of the tape, the greater is this tendency.
In magnetic tapes suffering this difficulty, not only is the poor appearance bothersome, but damage can occur to the edges of the tape. Also, the electromagnetic conversion characteristics of the tape may be degraded. The problem is particularly acute when high density recording is to be carried out, specifically, on a video magnetic tape where audio signals must be recorded near the side edges of the tape. Therefore, the above winding problem has been an extremely serious problem.
For this reason, in the conventional magnetic tape production process, the wound state is checked, for example, by visual inspection or the like, for all products after the above-mentioned take-up or retake-up steps. This requires much cost and time and creates a serious bottleneck in the production of magnetic tapes.
In order to improve the winding appearance to thereby reduce the need for manual checking, a system called "style winding", as illustrated in FIGS. 8 and 9, has been employed in magnetic tape take-up process in which the yield of products of good winding appearance is generally poor.
FIGS. 8 and 9 are the schematic perspective views each showing the arrangement in the vicinity of a tape winding body 2 at the tape-up side. In the arrangement shown in FIG. 8, a flexible endless belt 11 made of, for example, rubber, polyimide, or the like is rotatably held by rotary rollers 12, 13 and 14 so as to rotate together with a magnetic tape T. The flexible belt 11 elastically urges the magnetic surface of the tape in the radial direction of the tape winding body 2 to thereby determine the winding appearance of the magnetic tape T. In the arrangement shown in FIG. 9, a belt 15 made of a comparatively soft nonwoven fabric or the like is laid between one flange of the tape winding body 2 and a side edge of the magnetic tape T. This belt 15 is arranged so as to urge a lateral edge of the magnetic tape T to arrange the winding appearance of the magnetic tape T while the belt 15, supplied from a belt-feed side 16, is moved at a low constant speed while being held by a rotary roller 17 or the like and then taken up on a belt take-up side 18.
In both arrangements, however, the belt directly contacts the magnetic tape T, resulting in various problems such as the occurrence of drop-out due to fragments dislodged from the magnetic layer or peeled from the fabric of the belt, transformation of the tape due to application of inappropriate pressure to the tape, and damage to the tape at its lateral edges. Thus, sometimes these arrangements fail to accomplish the intended function. Further, the style winding mechanism has problems in terms of a high cost and the need for frequent operator intervention to replace the belt supply due to the high consumption rate of the belt material. Still further, the winding mechanism must be arranged such that, when the tape winding body 2 is replaced, the mechanism can be moved between operative and inoperative positions. As a result, the take-up apparatus is necessarily complicated in structure, and it takes a relatively long time to replace the tape winding body. Therefore, the tape winding time remains an obstruction to improving tape manufacturing productivity.
In current tape winding practice, various tape winding techniques are known, including the in-cassette, C-O and V-O take-up systems in which a magnetic tape is wound into the cassette at a final stage of cassette assembly. This technique is thus significantly different from the above-mentioned open take-up system in which the wound magnetic tape is inserted into the cassette after style winding of the tape.
As shown in FIGS. 10 and 11, a semi-finished product (generally called V-O, C-O, or the like) includes all parts other than the magnetic tape assembled into a cassette 23. The tape feed-out and take-up winding bodies 2 and 3 are connected together by a leader tape 10. The leader tape is drawn out and cut by a tape-up apparatus called an in-cassette winder. One cut end of the leader tape is spliced to an end of the magnetic tape to be wound into the cassette, while the other cut end of the leader tape is held by a suction member 22. The tape winding body 2 having the leader tape connected to the magnetic tape is rotated to take up a predetermined length of the magnetic tape T. Then, the magnetic tape is cut, and finally the cut end of the wound-up magnetic tape is spliced to the other cut end of the leader tape to complete the product.
In such an in-cassette take-up system, no part of the described tape winder mechanically contacts the tape winding body as the magnetic tape is wound. Therefore, the winding appearance of the finally wound tape depends on the physical properties of the tape itself and variations in cassette components, thereby making it completely impossible to control the winding appearance, resulting in an extremely poor yield of cassettes with a good winding appearance.
In this case, in order to improve the winding appearance, it has been attempted to use a roller 24 with a pair of upper and lower flanges 25a and 25b disposed at the inlet side of the cassette. The roller 24 applies a widthwise force to the magnetic tape as it is being wound into the cassette to thereby urge the magnetic tape to one side. With this arrangement, however, actually very little improvement in the winding appearance is achieved. Thus, prior to the invention there has been no effective measure to improve the winding appearance of the magnetic tape.